A light aircraft is flying over spectacular jungle terrain. On board is oil prospector Robert Harper (Massimo Foschi), his business partner Ralph (Ivan Rossimov), the pilot Charlie (Sheik Razak Shikur), and a young lady named Swan (Judy Rosly). There is much talk about inhospitable and harsh the jungle is which is apparently Malaysia. They are on their way to visit a oil prospecting party which has set up camp there.Upon landing, they find the area abandoned. They soon discover a native weapon covered with blood. Ralph is concerned, exclaiming that the weapon indicates the people who raided the camp are; "worse then natives. Judging the way this was made, they're still living in the stone age." Harper wonders into the jungle, while Ralph follows him and they both get lost. During their trek through the jungle, they discover the partially-decomposed corpse of one of the prospectors. Harper and Ralph manage to return to the airstrip where the seriousness of their predicament becomes apparently. But since they wondered off, it is too late for them to take off for darkness comes and they decide to sit out the night in the plane.Later that night, Swan unwisely decides to leave the plane so she can relive herself in the nearby bushes. She is captured by several unseen natives. The three men are all too scared to help even though they hear her screams, convincing themselves that they should stay put for the night and look for her in the morning when it is daylight.The next morning, Harper, Ralph, and Charlie set out into the jungle to look for Swan. Within minutes, Charlie springs a native trap and is horribly impaled by a spiked ball. Momentarily losing his mind at the sight of his dead friend, Harper runs blindly into the jungle followed by Ralph. This time, they really do get hopelessly lost. After witnessing a group of native warriors eating the remains of Swan, the two men continue on and come across a river. They decide to make a raft to float downstream and hopefully make it back towards the airstrip. During the ride, their raft overturns on some rocks, and Harper is left alone as he grabs onto a shore rock as Ralph is swept away by the current.Over the next day-and-a-half, Harper wonders aimlessly through the trackless and inhospitable jungle dealing with insects, snakes, and other wildlife. Desperately hungry, he unwisely gorges himself on mushrooms, starts to hallucinate and soon passes out. When he wakes up, he finds himself surrounded by dozens of long-haired, savage natives, warily poking their spears at him. The natives take the captive Harper back to their camp which is a huge cave dwelling place.The savage natives tie up Harper where they strip him naked, and string him up in a harness and hoist him into the heights of the misty cave. Having seen him arrive by airplane, the natives apparently believe that he has the power to fly, so they let him freefall 60 or more feet before he is abruptly halted by the harness and rope device to which he is attached to. His painful ordeal continues again and again until he passes out, while the natives wave their arms and hoot hellishly.Over the next several days, Harper is imprisoned in a cage and forced to watch the natives and their lifestyle. He is fed dead and rotting small animals, as well as subjected to further torture and humiliation. Harper watches the natives bring a captive warrior from a rival tribe and have him slowly killed by tying the warrior's arm to an army ant hill where they ants slowly eat the captive warrior alive.Harper befriends one of the very few women of the tribe, a native woman who, despite the language barrier, introduces herself as Pulan (Me Me Lai). But she is held in check by Harper's guards who forbid her from talking to their prisoner. Harper soon becomes clear at what the natives have in store for him: they apparently want to use him as bait to catch a very large meal like a crocodile the natives catch after using a bird to catch their prey. He is forced to watch the natives kill, skin, and eat the crocodile among other various animals from a python to a tree monkey.One evening, Harper decides to make his move. He tricks Pulan into opening his cage, and then grabs her as well as bludgeoning the guard watching him. Harper escapes from the cave with Pulan as a hostage/guide. When she tries to escape, he attacks and savagely rapes her, cementing their bond. Being violated, Pulan apparently decides, by her tribe's custom, to become his companion and servant.One day during a sudden rainstorm, Harper and Pulan come across a cave, and find Ralph, who is alive and well and been hiding out from the natives this entire time. However, Ralph's mobility is impaired by a festering leg wound which he got during the overturning of their raft. Both men decide to force Pulan to lead them back to the airstrip to their plane so they can return home. The next day, the three of them set off as Ralph explains more about jungle survival. At one point, Ralph ensnares a cobra, milks its venom, and applies it to the end of Harper's makeshift lance.Pulan's hesitation about traveling through cannibal country is soon justified when they are surrounded by dozens of natives. In the chase, Ralph is hit in the chest by a spear, while Pulan is also hit and falls prey to her fellow native people and quickly killed. Harper is forced to help Ralph along as Pulan is gorily beheaded, sliced open, and gutted. Hot coals are place into her gaping chest cavity and her flesh is eaten.By the time the cannibals catch up to the two men, who make it to the river, Ralph is weakening fast from his fresh wound and can no longer defend himself. So, Harper is forced to fight against one of the cannibal natives. Harper kills his opponent by stabbing him with the poisoned lance. His assimilation into the savage ways of the jungle is completed when in devastating fashion, he disembowels his foe, pulls out an internal organ, and eats in front of the native warriors who watch the whole thing. Following this show of strength, the intimidated natives slowly back away and allow Harper to continue on his journey, carrying his barely conscious friend with him. Harper and Ralph finally follow a track from the river and make it back at the airstrip with the plane still sitting in its place. As the natives look on from a respective distance, Harper places Ralph in back of the plane, starts up and engine and takes off, finally free from his ordeal. But in the back seat, Ralph after hearing from Harper that they have made it and are on their way home, kneels over and dies having succumbed to his wounds.